zero.onclick = function(){
    zero.value = 0;
}
one.onclick = function(){
    one.value = 1;
}
two.onclick = function(){
    two.value = 2;
}
three.onclick = function(){
    three.value = 3;
}
four.onclick = function(){
    four.value = 4;
}
five.onclick = function(){
    five.value = 5;
}
six.onclick = function(){
    six.value = 6;
}
seven.onclick = function(){
    seven.value = 7;
}
eight.onclick = function(){
    eight.value = 8;
}
nine.onclick = function(){
    str = nine.value;
}


add.onclick = function(){
    add.value = "+";
}
mulit.onclick = function(){
    mulit.value = "*";
}
diff.onclick = function(){
    diff.value = "-";
}
except.onclick = function(){
    except.value = "/";
}

clean.onclick = function(){
    str= "";
}
decimal.onclick = function(){
    decimal.value = ".";
}
sum.onclick = function(){
    sum.value = "=";
}